I've read spoilers (because I'm impatient like that) that the reason FL hated flowers because after the Ex's parents died and she took over as temporary Lord, she once tried to arrange wreaths and bouquets for Ex's household to cheer him up during the mourning. She knew Ex secretly loved flowers, but shy about it.
Ex got home, saw the flowers and was happy for a sec, but his pride was bigger than his thanks. He ordered the flowers to be burned. FL went to sleep with the house smelling of burning flowers.